In a typical cellular wireless communication system, it is often desirable to determine the location of a mobile station such as a cellular telephone. The location of a user's mobile station can facilitate various services, such as emergency response and commercial information services (e.g., navigation or reporting of nearby points of interest), among others.
One increasingly common way to determine the location of a mobile station to analyze signals that the mobile station receives from Global Positioning System (GPS) satellites. In practice, when it becomes necessary to determine the location of the mobile station, the mobile station may employ a GPS receiver to receive signals from GPS satellites in the sky over the mobile station. The mobile station, or a network server to which the mobile station reports, may then analyze information about those signals in order to compute with a fairly high level of accuracy the location of the mobile station. This computed location may then be passed along to a location based service provider, such as an emergency service center or a commercial information service center, or may be used by the mobile station itself or in various other ways, to provide useful location-based information or functionality.
One problem with using GPS signals to determine mobile station location is that a mobile station may not always have a clear enough view of the sky to receive the necessary GPS signals. For instance, when a mobile station is inside a house or other building, the structure of the building may prevent the GPS signals from reaching the mobile station's receiver. In situations like that, other more rudimentary forms of location determination may then be used. However, further improvement is still desirable.